STUDY ON SYSTEMATIC BOLTS EFFICACY IN ARCH OF SOFT ROCK TUNNEL BY THE SHALLOW MINING METHOD

The systematic bolts are often arranged in the soft rock tunnel arch, but their efficacy is different in the different geological conditions and support patterns.The researches on the efficacy of the systematic bolts in the arch of soft rock underwater highway tunnel by the shallow mining method were very rare.Therefore, as an example of Liuyanghe tunnel which was constructed by the shallow mining method in Changsha, the systematic study on tunnel arch systematic bolt with respect to axial force, internal force of primary liner, safety factor of digging and the effects on bolt by groundwater seepage to soft rock were performed by the theoretical analysis, the numerical simulation, and the field test.The results showed that the efficacy of the arch systematic anchor bolts of the Liuyanghe tunnel, under soft rock geologic environment, was not significant and their actions were less.It was suggested that the foot anchoring bolts were installed in shaped steel of upper bench, and the arch systematic bolts could be cancelled.The research results were applied in practice, which had significant benefits.